squirreledEditable declared in wrong scope

The idea is that squirreledEditable is a global variable, here limited to the
plugin scope by requirejs, that helps us out during the times when
Aloha.activeEditable is misteriously cleared. Moving it to plugin scope appears
to be the correct fix then.
Add title of document to saved html.

Upstream code looks for a title in the html document header. This code has
never worked like that, but it seems upstream now expects it. It does make
the html more correct, since strictly speaking a <title /> is required, so
I'm adding it here.